In traditional lithographic printing presses, ink and dampening fluid are applied by rollers onto a lithographic printing plate. The printing plate is mounted onto a plate cylinder which rotates the printing plate past the ink and dampening rollers. The printing plate contains oleophilic and hydrophilic areas. The oleophilic areas are arranged according to the desired image which is to be printed onto media such as paper. The oleophilic areas attract the oil-based ink. Nonprint areas on the printing plate attract the water-based dampening fluid and repel the ink.
In order to achieve satisfactory printing, a proper balance must be achieved between the amount of dampening fluid applied to the plate versus the amount of ink that is applied. If too much dampening fluid is applied, then the print areas look faded, as the dampening fluid begins to be applied to the oleophilic areas. If too little dampening fluid is applied, then the ink appears in nonink areas. Much effort has gone into the systems that apply dampening fluid to a plate, in order to achieve this balance.
One type of inking system that is used is referred to as waterless printing by the printing industry. In waterless printing, dampening fluid is not used. Instead, only special inks are applied to the plate on the plate cylinder. The nonprint areas of the plate are coated with a silicone rubber film, which will not attract the ink under normal operating conditions. In order to maintain the ink away from the nonprint areas of the plate, the ink must be maintained within a certain temperature range. For example, some inks must be maintained within just a few degrees of 80 degrees Fahrenheit. If the ink becomes too cool or too warm, then its viscosity changes and the proper application of ink to the plate becomes increasingly difficult.
Printing presses are subjected to wide temperature ranges. For example, when a press is started first thing in the morning, it typically is below the desired ink temperature range for waterless printing. This is because the press has been sitting all night and has had a chance to cool off. As the press begins to operate, heat is generated by the friction between its rollers and also by the electric drive motors. The heat that is generated causes the temperature of the ink to increase beyond the desired temperature range for waterless printing. With the ink being above the desired temperature range, unsatisfactory printing results.
It is therefore desirable to provide a temperature controlled system for maintaining the temperature of the ink in a waterless printing system within the desired range.